Alpha-mannosidosis: Alpha-mannosidase Enzyme Analysis

Clinical Information

Alpha mannosidosis is an autosomal recessive lysosomal storage disorder caused by a deficiency of alpha-mannosidase enzyme activity. This condition demonstrates variable expressivity with three clinical phenotypes described as mild (type I), moderate (type II), and severe (type III), with onset varying from prenatal loss with type III to after 10 years of age with type I. Features can include mild or moderate intellectual disability, abnormalities in motor function, hearing loss, dysostosis multiplex, immunodeficiency, cataracts/corneal opacities, hepatosplenomegaly, and characteristic facial features.

Technical Information

Enzyme activity is measured using a 4-methylumbelliferyl (4-MU) substrate.

Specimen Requirements

• Accepted sample types for this test include DBS, fibroblasts, and leukocytes.
• DBS: Approximately 75 uL of blood should be applied to each of the five circles on filter paper dried blood spot card. Allow blood to dry for at least 4 hours before shipping.
• Fibroblasts: Tissue sample should be stored in sterile culture media; cultured fibroblasts should be sent in two T25 flasks. Do NOT place tissue in formalin or formaldehyde. Do not freeze tissue.
• Leukocytes: A minimum of 5 mL whole blood (7-10 mL preferred) collected in a sodium heparin tube.

Transport Instructions

• DBS: Ship DBS card at ambient temperature
• Fibroblasts: Ship tissue sample or cultured fibroblasts at ambient temperature
• Leukocytes: Whole blood should be shipped at ambient temperature. If leukocytes are being isolated at another laboratory, the pellet should be frozen after specimen processing and shipped frozen on dry ice.